PARIS -- The French have a new weapon in their tireless war against American cultural imperialism: Asterix and Obelix. The two comic-book heroes of ancient Gaul are springing to life on screen in the most expensive French-language production yet.

The 280-million-franc ($48.4 million) "Asterix and Obelix vs. Caesar" opened Wednesday in France and Belgium. After weekend spreads of more than a dozen pages in magazines like Paris Match and Le Figaro Magazine and nightly appearances of the film's stars on the evening...